Tiamat

[ Tiamat ]
Gargantuan fiend, chaotic evil
Armor Class 25 (natural armor)
Hit Points 615 (30d20 + 300)
Speed 60 ft., fly 120 ft.
STR
30 (+10)
DEX
10 (+0)
CON
30 (+10)
INT
26 (+8)
WIS
26 (+8)
CHA
28 (+9)
Saving Throws Str +19, Dex +9, Wis +17
Skills Arcana +17, Perception +26, Religion +17
Damage Immunities acid, cold, fire, lightning, poison; bludgeoning, piercing, and slashing from nonmagical attacks
Condition Immunities blinded, charmed, deafened, frightened, poisoned, stunned
Senses darkvision 240 ft., truesight 120 ft., passive Perception 36
Languages Common, Draconic, Infernal
Challenge 30 (155000 XP)
Discorporation.
Innate Spellcasting (3/Day).
Legendary Resistance (5/Day).
Limited Magic Immunity.
Magic Weapons.
Multiple Heads.
Regeneration.
ACTIONS
Multiattack.
Claw.
Tail.
Frightful Presence.
LEGENDARY ACTIONS
Bite.
Black Dragon Head: Acid Breath (Costs 2 Actions).
Blue Dragon Head: Lightning Breath (Costs 2 Actions).
Green Dragon Head: Poison Breath (Costs 2 Actions).
Red Dragon Head: Fire Breath (Costs 2 Actions).
White Dragon Head: Cold Breath (Costs 2 Actions).

This full creature's stat block is not available (not OGL).

Tiamat is the dragon goddess of evil.
Adventures (Tyranny of Dragons)